This application claims the benefit of Korean Application No. 2001-76973, filed Dec. 6, 2001, in the Korean Industrial Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an ink-jet printer, and more particularly, to a sheet feeding apparatus of an ink-jet printer to provide sheets of paper loaded in a cassette to a main body of the printer.
2. Description of the Related Art
In general, ink-jet printers are output devices to print images or characters by injecting ink onto a sheet of paper while an ink cartridge mounted on a carriage reciprocates horizontally.
In the conventional ink-jet printers, paper is transferred according to one of two methods. First, a sheet feeding cassette in which sheets of paper are loaded is installed at an angle in the rear of the main body, so that the paper is transferred to a printing unit by a pickup roller, printed, and then ejected through a sheet exhaust unit disposed in front of the main body. Second, the sheet feeding cassette to load sheets of paper is located under the main body of the printer and the paper is transferred to the printing unit by the pickup roller and printed, and then ejected through the sheet exhaust unit located above the sheet feeding cassette. The sheet feeding cassette is detachably coupled to one side of the ink-jet printer and a plurality of sheets of paper are loaded therein.
In particular, in the ink-jet printer adopting the second method of transferring paper, the sheets of paper are supplied inside the ink-jet printer one by one as the pickup roller rotates while contacting the upper surface of the paper disposed at the top of a stack of paper in the sheet feeding cassette during printing. By repeating the sheet pickup step performed by the pickup roller, the number of papers loaded in the sheet feeding cassette decreases.
However, even when the number of papers loaded in the sheet feeding cassette is reduced, to have the sheet pickup operation continuously performed by the pickup roller, the pickup roller and the paper must contact each other. To meet this condition, a vertically acting force must be applied to the pickup roller or the paper so that the pickup roller is pressed against the paper or the paper is pressed against the pickup roller.
There are two methods of applying a vertical force to the pickup roller or the paper. First, the pickup roller is installed to be fixed at a predetermined position above the paper, and an elevating plate installed at the sheet feeding cassette to be capable of moving up and down closely presses the paper toward the pickup roller. Second, the pickup roller is closely pressed toward the stacked paper with the weight of the pickup roller assembly itself.
As the paper pickup operation is continuously performed by the pickup roller according to the above-described methods, even when all of the sheets have been fed and no paper remains, the pickup roller continues to perform the sheet feeding operation according to a printing signal. Thus, the pickup roller rotates in direct contact with the elevating plate or the sheet feeding cassette.
As a result, the pickup roller can be damaged by friction. Also, since an excess force is applied to a gear train of the pickup roller assembly connected to the pickup roller to transfer power, the gear train may be damaged.
Accordingly, it is an object of the present invention to provide a sheet feeding apparatus of an ink-jet printer having a buffer member to prevent the pickup roller from being damaged after all of the sheets of paper have been fed.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
The foregoing and other objects of the present invention are achieved by providing a sheet feeding apparatus of an ink-jet printer in which sheets are provided in a main body of the printer, the apparatus including a cassette to accommodate the sheets of paper, detachably provided in the main body of the printer; a pickup roller portion to pick up the accommodated paper; a pickup roller rotating in contact with the picked-up paper to feed the paper into the main body; and a buffer member to prevent damage to the pickup roller portion occurring when the pickup roller continuously performs a pickup operation when all of the paper has been fed from the cassette, the buffer member including a guide portion provided in the cassette, a stop portion having first and second portions protruding from the cassette towards each other to support the pickup roller when all of the paper has been fed from the cassette, a pad installed between the stop portion and the guide portion to slide, and an elastic unit to apply a restoration force to the pad in a direction opposite to a direction in which the paper is supplied into the main body of the printer.